This work focuses on the analysis of structure function relationships between identified pre and postsynaptic neurons in a mapped sensory system. We plan to use the IVEM to do serial reconstructions of primary afferents and sensory interneurons to determine the location, number and type of synapses on and between these cells. We will also use 3-D reconstructions using serial tomography to estimate the volume and functional dimensions of synapses in specific anatomical regions of both cell types. Measurements of the dimensions of specific regions of interneurons will be used to estimate membrane surface area for compartmental modeling studies. Since these cells are quite large and it is important to sample many different areas of the cell, conventional thin section microscopy would make this task extremely time consuming and difficult. The ability to use thicker sections in the IVEM will enable us to obtain this information rapidly and with the necessary accuracy. The IVEM studies will compliment an ongoing analysis of this system at the light microscope level. We also plan to use the IVEM to study the formation and growth of new synapses on primary afferents during development and in animals reared in specific stimulus environments. Work on this project was interrupted briefly while Drs. Jacob and Miller moved to Montana to establish the new Center for Computational Biology, of which they are co-directors. Nevertheless, we have begun analysis of fluorescently labeled specimens on the confocal microscope and hope to extend this analysis to the electron microscopic level in the near future. In addition, we are investigating software for performing automated skeletonization.